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Originally Posted by Augi
Martian, what news is there of that meteor/asteroid that will pass so close to Earth sometime in the near future that it will come back in 7 years?
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I suspect the object you're thinking of is Apophis, aka 2004MN<sub>4</sub>. Apophis created a stir back in 2004 because it passed near Earth and projections put it on a collision course with Earth ca 2029. That netted it a 4 on the Torino scale, the highest threat rating granted any Near Earth Object to date. Subsequent data collection showed that it would most likely be a miss (albeit a fairly close one, relatively speaking) and today Apophis is back at a 0, indicating negligible risk.
In keeping with the tone of the piece, I will admit I've exaggerated some of the threats involved here. After all, where's the fun in saying 'this
could hypothetically happen, but it's not very bloody likely'? The aforementioned object slated to strike Earth ca 2900 is named 1950 DA, and has the dubious distinction of being the only object out there currently with a threat rating higher than 0, as it's at a 1 (the Torino scale, as a point of interest, increments only in integers and goes from 0 to 10, making a 1 the lowest possible value that's
not 0). Essentially, based on the eccentricity of it's orbit, 1950 DA has a possibility of going one of two ways; if it goes one direction, it passes no nearer to us than Mars; the other way it comes closer and has a chance of hitting us. In 2900. Assuming our predictions are correct.
Really folks, not something to lose to much sleep over. But smile all the same, because even with all this we
could all be dead tomorrow.
Also, just to straighten out the terminology:
A meteoroid is a very small object that travels through the solar system; the generally accepted threshold is 10m, smaller than that it's a meteoroid. Larger, it's an asteroid. Meteoroids beget meteors when they hit the Earth's atmosphere and burn brightly; a shooting star is a meteor. Meteors in turn beget meteorites when they're travelling slow enough or are large enough for part of the object to make it through the atmosphere and to the surface of the Earth; a meteorite is a grounded meteor. And tektite, for the geologists out there, is a type of rock formed when a meteorite or other object impacts with enough force to deform the surface of the Earth. The energy from the meteorite is converted largely into heat, which melts the rock. When the rock cools it reforms as tektite.
Asteroids are larger than meteoroids but smaller than dwarf planets. The exact distinction of what makes a dwarf planet and what makes an asteroid gets a bit technical, but that's the long and short of it. And planets are a step up from dwarf planets. Moons are objects in orbit around a planet, of which there are dozens currently known, the bulk of them belonging to Jupiter and Saturn.
The most numerous type of object in the solar system by far and away are asteroids. The only other type of object that does not fall into one of the above categories is the comet, which is distinguished by it's tail. A comet's tail is the result of it's composition, which undergoes a thermal reaction as it approaches the Sun.
And I think that about covers it.